ftpd

NAME

SYNOPSIS

ftpd [-dl] [-ttimeout] [-Tmaxtimeout]

FLAGS

Debugging information is sent to the syslogd daemon (see
syslogd(8)).
Each FTP session, as well as additional
information, such as the file name retrieved or stored, the number of
bytes, and the attempted logins that failed, is sent to the
syslogd daemon (see syslogd(8)).
The inactivity time-out period will be set to time-out seconds.
The maximum timeout period allowed may be set to timeout seconds
with this option.

SECURITY NOTE

This security-sensitive command uses the SIA (Security
Integration Architecture) routine
as an interface to the security mechanisms. See
matrix.conf(4) for more information.

DESCRIPTION

The
ftpd
command is the DARPA (Defense Advanced Research Projects Agency)
Internet File Transfer Protocol
server process. The server uses the TCP protocol
and listens at the port specified in the FTP
service specification; see
services(4).

The ftpd command includes two flags to control the
information logged for the ftpd daemon.
If the -d flag is specified, debugging information is logged.
If the -l flag is specified,
each ftp session, along with data for login failures and
file operations, is logged.
Refer to the syslogd(8) reference page for information on system
log files.

The FTP server
will time out an inactive session after 15 minutes.
If the -t flag is specified,
the inactivity time-out period will be set to time-out seconds.
A client may also request a different time-out period;
the maximum period allowed may be set to time-out seconds with the
-T flag. The default limit is 2 hours.

The FTP server currently supports the following ftp
requests; case is not distinguished:
Description
Abort previous command
Specify account (ignored)
Allocate storage (vacuously)
Append to a file
Change to parent of current working directory
Change working directory
Delete a file
Give help information
Give list files in a directory (ls -lgA)
Make a directory
Show last modification time of file
Specify data transfer mode
Give name list of files in directory
Do nothing
Specify password
Prepare for server-to-server transfer
Specify data connection port
Print the current working directory
Terminate session
Restart incomplete transfer
Retrieve a file
Remove a directory
Specify rename-from file name
Specify rename-to file name
Nonstandard commands (see next section)
Return size of file
Return status of server
Store a file
Store a file with a unique name
Specify data transfer structure
Show operating system type of server system
Specify data transfer type
Specify username
Change to parent of current working directory (deprecated)
Change working directory (deprecated)
Make a directory (deprecated)
Print the current working directory (deprecated)
Remove a directory (deprecated)

The following nonstandard or UNIX compatible commands are supported
by the SITE request:
Description
Change umask (for example, SITE UMASK 002)
Set idle timer (for example, SITE IDLE 60)
Change mode of a file (for example, SITE CHMOD 755 filename)
Give help information (for example, SITE HELP)

The remaining ftp requests specified in Internet RFC959 are
recognized, but not implemented.
MDTM and SIZE are not specified in
RFC959, but will appear in the next updated FTP RFC.

The ftp server will abort an active file transfer only when the
ABOR command is preceded by a Telnet Interrupt Process (IP)
signal and a Telnet Synch signal in the command Telnet stream,
as described in Internet RFC959.
If a STAT command is received during a data transfer, preceded
by a Telnet IP and Synch, transfer status will be returned.

The ftpd command
interprets file names according to the ``globbing''
conventions used by the C shell (see csh(1)).
This interpretation allows users to utilize the metacharacters ``*?[]{}~''.

The ftpd command authenticates users according to four rules:
The username must be in the password database, /etc/passwd,
and not have a null password. In this case, a password
must be provided by the client before any file operations
may be performed.
The username must not appear in the /etc/ftpusers file.
The user must have a standard shell returned by the
getusershell() call (see getusershell(3)).
If the username is anonymous or ftp, an
anonymous ftp account must be present in the password
file (user ftp). In this case, the user is allowed
to log in by specifying any password (by convention this
is given as the client host's name).

The ftp command uses the default Type-of-Service values
recommended by RFC1060, which are as follows:
Low delay
High throughput

Anonymous FTP Configuration

If you are creating an anonymous FTP account, ftpd
takes special measures to restrict the client's access privileges
when the user logs in. The server executes a chroot call
(see chroot(2)) to the home directory of the ftp user.
In order that system security is not breached, it is recommended
that you adhere to the following rules when creating directories and
files in the ftp subtree:
Make the home directory owned by the superuser (root) and unwritable by anyone.
Make this directory owned by the superuser and unwritable by
anyone. The ls program (see ls(1))
must be present to support the list command.
This program should have mode 111.

Copy the ls program from /sbin/ls. This is the
statically linked version of the ls command, which does not require
shared library support. Be sure
to copy the static version of ls from the /sbin directory,
not the shared version from the /usr/bin directory.
Make this directory owned by the superuser and unwritable by
anyone. The passwd and group files (see passwd(4) and
group(4) )
must be present for the
ls command to be able to produce owner names rather than numbers.
The password field in the
passwd file
is not used, and should not contain real encrypted passwords.
These files should be mode 444.

In this environment,
the sia subdirectory (which you can copy from /etc/sia)
must also be present for the ls command to be able to produce
owner names rather than numbers.
Make this directory mode 777 and owned by ftp. Users
should then place files that are to be accessible via the
anonymous account in this directory.

You can configure these values by specifying them in the
/etc/iptos file. For more information, see iptos(4).

FILES

Specifies the command path.
Contains the list of unauthorized users.

CAUTIONS

The anonymous account is inherently dangerous and should be
avoided when possible.

The server must run as the superuser to create sockets with privileged
port numbers. It maintains an effective user ID of the
logged in user, reverting to the superuser only when
binding addresses to sockets. The possible security holes
have been extensively scrutinized, but are
possibly incomplete.